The subject of the present invention is a machine for coiling or winding a continuous flat element to form coils or reels.
Coiling or reel-winding machines are used in a great many branches of industry in which the machines and methods involved culminate in the continuous manufacture of a flat element of some arbitrary width and variable thickness. The flat elements produced by the manufacturing lines have to be coiled or wound so that they can easily be transported to subsequent transformation stages.
This is, in particular, the case in industrial methods and machines for the continuous manufacture of woven fabrics, paper, plate, plastic films and sheets, nonwovens etc. For reasons of simplicity, it is the term "sheet" which will be used hereafter to denote these different types of flat element. In the domain of plastics, the winding machines are used as a matter of course at the end of the manufacturing lines that manufacture plastic film in materials as diverse as polypropylene, polyester, PVC, polyethylene, complex coextruded sheets, etc.
Most of these industrial methods run continuously, the machines practically never being shut down, except for maintenance operations which are several weeks, if not several months, apart.
Furthermore, for them to remain easy to handle, and for other reasons associated with coiling or winding machine techniques, the possibilities of increasing the diameter of the coils or reels of coiled or wound product are not unlimited. It is therefore necessary that the coiling or winding machines used on continuous manufacturing lines be equipped with devices which make it possible, without interrupting production, to change over from a full coil or reel, when the latter has reached the intended diameter, to a new empty coil or reel. It is obvious that such an operation which has to be performed continuously, requires that at a given moment, the sheet be cut at the line production rate and led by appropriate devices onto the core of the new coil or reel back onto which it is to be fed.
It is these devices which are known as sheet cutting systems for automatic coil or reel changeover on coiling or winding machines.
Coiling or winding machines that allow this type of application all exhibit a certain number of common features, which are as follows:
As FIG. 1 shows, several coiling or winding spindles (1), generally two of these, are each equipped with their drive device and are mounted securely on a rotary assembly known as a turret (2) mounted on a stand (3).
At a given moment, each spindle (1) with its associated drive device receives the sheet (F) arriving continuously from the production line, the drive system and its control module delivering the spindle the torque needed for the sheet to be driven at the desired speed and under the desired tension. The devices needed to regulate the torque are either dancing rollers, or electronic tension gauging systems situated upstream of the spindle (1) and tasked with continuously measuring the tension in the sheet (F) so as to automatically control the motor as a function of a pre-established coiling or winding requirement.
In other types of coiling or winding machine, which will be mentioned later, the spindle itself is not driven, but it is a contact roll (4), which is itself driven, which delivers the torque needed for coiling or winding.
When the amount of product coiled or wound on a spindle is such that the maximum diameter has been reached, then, through an operation of rotating the turret (2), without cutting the sheet (F), the empty spindle, which in the meantime has been brought up to the desired speed by its own regulation system, comes into contact with the sheet (F) that is to be coiled or wound, the full coil or reel then finding itself in the so-called off-loading position, but continuing to drive the product, as shown in FIG. 1.
It is at this instant that the automatic cutting device comes into operation to allow the sheet to be moved over from the full coil or reel onto the coil or reel back onto which it is to be fed, without any reduction in production speed.
The way in which this device is constructed depends greatly on the way in which the components upstream of the turret/spindle assembly are constructed, components whose function it is to feed through the product that is to be coiled or wound in a suitable way while at the same time allowing the drive devices to be regulated.
These drive devices generally consist of one or more rolls each fulfilling clearly defined functions and which are generally secured to a moving carriage (5) allowing the abovementioned rolls to maintain a constant geometric arrangement as the diameter of the coil or reel increases as coiling or winding progresses.
FIG. 2 depicts an alternative form of the machine of FIG. 1.
Such machines are used for winding very wide plastic sheets (up to 8 and 9 meters wide) of thin film of between 5 and 100 microns thick, but generally between 10 and 30 microns thick, and at speeds that can be as much as several hundred meters per minute.
As FIG. 2 shows, to wind this type of product, it is generally necessary for the carriage (5) to carry at least two rolls, of which a first roll (6), known as the tension-measuring roll, is equipped with an electronic gauge for continuously measuring the tension in the sheet (F), or is preceded by a dancing roller which fulfils the same function. This roll (6) must be positioned in such a way that the sheet arrives at the roll in a horizontal position (either from above or from below) so that, as the carriage moves as a result of the increase in the diameter of the reel, the angle of wrap of the sheet around the roll is not altered so that the tension reading is not disturbed by any change in wrap angle.
A second roll, known as the contact roll (4) is also needed to guide the sheet to the coiling or winding point. There are two types of coiling or winding commonly used--so-called contact coiling or winding, as shown in FIG. 3, during which the contact roll exerts light pressure on the coil or reel that is being coiled or wound, so as to expel the air which might otherwise become trapped in great quantities in the coil or reel because of the speed at which the sheet is coiled or wound, and coiling or winding known as "gap" coiling or winding, as shown in FIG. 4, in which the contact roll (4) is a short distance that is kept more or less constant away from the coiling or winding point. This type of coiling or winding is preferred when the speed is low because the risk of trapping air is then low, or alternatively when the thickness of the product that is to be coiled or wound is not very uniform and operation of the contact type would be liable to damage the coiled or wound product.
In simplified devices, just one roll is used, tension measurement taking place upstream of or at the entry to the coiling or winding machine.
In more complicated devices, either dancing rolls or so-called smoothing rolls (8), which are also mounted on the carriage (5), are added to the two rolls mentioned earlier.
The sheet, preferably fed in horizontally, may pass either over or under the set of rolls mounted on the carriage. This choice has very substantial consequences on the nature of the cutting system.
If the sheet is fed in from underneath the rolls on the carriage, it will naturally be made to pass over the spindle back onto which it is to be fed. In the reverse scenario, the sheet will pass under the spindle back onto which it is to be fed.
This direction of path therefore has a direct influence on the position of the cutting systems which, in traditional systems representing the state of the art, have, of necessity, to be on that side of the spindle past which the sheet passes.
FIG. 5 shows a coiling or winding machine equipped with a cutting device. This cutting device has to be operated automatically when cutting is desired, cutting having to be achieved in such a way that it disrupts the travel of the sheet as little as possible, the cutting point having to be chosen in such a way that the sheet, immediately after cutting, or, in the case of gradual cutting, the point corresponding to the start of the cut, can easily coil or wind around the spindle (1) back onto which it is to be fed so as to start that coil or reel. To achieve this objective, it is generally necessary for the cutting device to have wrapping rollers (9) bringing the sheet (F) in near to the spindle (1) onto which it is to be fed. The device must provide, in addition to the cutting system with a fixed blade (10) or moving cutters, means of guiding the sheet against the new spindle and which are either air jets or systems of brushes, or so-called electrostatic systems (11) generating electrostatic charge at the surface of the sheet to make sure that the cut sheet contacts the metal spindle back onto which it is to be fed. In some instances, adhesive tapes or possibly vaporized liquid jets are used to ensure reliable contact.
The multitude of functions to be fulfilled by the cutting device means that this device is generally complicated and bulky and that it only works if the layout in space of all the elements that make up the spindle back onto which the sheet is to be fed, and the cutting system proper, are very clearly defined.
This is why these devices are generally situated in close proximity to, but just after, the spindle back onto which the sheet is to be fed. This is because the position of this spindle is clearly defined by virtue of the system comprising stand (3) and turret (2), the position of the sheet (F) is clearly defined by virtue of the moving carriage (5), and finally, the wrapping rollers (9) mounted on the automatic cutting device allow the sheet (F) to be positioned practically independently of the diameter of the finished coil or reel.
This last point has a highly detrimental consequence on the use of the production lines because it imposes the fact that cutting and coil or reel changing can be performed automatically only onto an empty spindle, so that the geometry indicated above is perfectly defined.
Now, in almost all industrial processes that employ very wide thin sheets at high speed, there are a certain number of unpredictable production incidents which sometimes lead to breakages of the sheet, for example as a result of the presence of a foreign body in the sheet or as a result of a handling error on the manufacturing line, or any other arbitrary reason. In general, as the production conditions can be re-established almost instantly, the sheet becomes available again and ready to be coiled or wound very soon after the breakage. If this breakage has occurred very shortly after a coil or reel has been begun, this coil or reel will not have a very large diameter, and the obligation to use the automatic cutting device only in proximity to an empty spindle means that it is compulsory, with the current design of device, to restart the coil or reel on a new spindle. When this occurs, the loss of production that the break represents, and which is generally small, is increased dramatically by the fact that the coil or reel begun previously is not of a large enough diameter that it is economically viable to use it in subsequent transformation processes.
This aspect may be further exacerbated if, as unfortunately does occur sometimes, a second breakage then occurs before the new coil or reel has reached an economically viable diameter. In this case, it is the entire production corresponding to two started, but not full enough coils or reels, which is lost.